Reply To: Kylchap Exhaust Systems

[Chris Corney]

There is another question that I’ve been mulling over.
Assuming the smokebox gas impinges on the steam jet at an angle, it will be possible the resolve the velocity into two vectors, one parallel with the steam jet, and the other one perpendicular.
Now the Kinetic Energy (KE) of each component can be calculate from the equation KE = ½ mv2
And as the two values of KE are proportional to the square of velocity and the vectors are at right angles to one another, Pythagoras tells us that summing the two together will give the KE of the resultant flow (which is what you would expect).
Now considering the KE of the perpendicular flow in isolation, it would be straight forward to obtain a value of velocity by dividing the volume flow by the surface area of the steam jet.
The question is whether this is a significant quantity. The KE has to be generated by the exhaust acting as an ejector pump, and then the energy is just lost as heat, which will have further detrimental effects.
Basically I’m wondering what the advantage of the Kylchap was, or in other words why Chapelon, Gresley and others went to the trouble of using it.
I’m thinking that the design of the Kylchap, with the various cowls and mixing areas would have maximised the effective surface area of the steam jet, and therefore minimised the “lost” KE of the perpendicular moment of flow. Does this make sense?